1. Field of the Invention
This invention relates, in general, to the treatment of infants and, more particularly, to optically transparent radiant heat sources for use with or incorporation into infant incubators to provide radiant heat to an infant being treated in an infant incubator.
2. Description of Related Art
Infant incubators are used in the treatment and maintenance of weak, sickly, premature or low birth weight infants in order to maintain infant body temperature and allow the infant to develop. Infants may lose heat in four ways: through evaporation, convection, conduction and radiation. Conductive heat loss in an infant is usually considered negligible, since the mattress upon which the infant is placed is generally an excellent insulator, and, therefore, such net heat loss is small. Evaporative heat loss is dependent upon the incubator air temperature and infant skin temperature differential, as well as the relative humidity of the incubator air and the air velocity across the infant's skin. Evaporative heat loss is often referred to as insensible water loss, and can be controlled by controlling the air flow characteristics of the incubator design, the incubator air temperature, and by adding humidity to the incubator air. Convective heat loss is also a function of the incubator air temperature and infant skin temperature differential. Radiative or radiant heat loss is a function of infant skin temperature and incubator wall temperature differential. Radiant heat loss is typically the major source of heat loss, except in the very first days in the life of a very premature, very low birth weight infant, when evaporative heat loss (insensible water loss) may be greater.
The amount of heat lost by any of the ways mentioned is dependent upon incubator design and the infant's metabolism. The desired objective of an incubator environmental control system is to provide a thermal environment which will place minimum demand on the infant's metabolism to maintain body temperature at its preferred level. Typically, this state of minimum metabolic demand is assumed to be achieved when an infant's skin temperature is maintained within a prescribed normal range.
Radiant heat loss from the infant may be reduced by minimizing radiant heat loss through the walls of the incubator. This is because the primary source of radiant heat loss in an incubator is cold incubator walls. Minimization of radiant heat loss through the incubator walls can be accomplished in either of two ways. First, by increasing the wall temperature of the incubator, the temperature differential between the infant and the incubator walls may be minimized. Second, by adding radiant energy directed to the infant through the walls of the incubator, the radiant heat lost by the infant may be balanced with the heat gained from the radiant source.
Hence, radiant warming has been used to add radiant energy to the infant. In some instances, incubators, such as the one shown in U.S. Pat. No. 3,858,570--Beld, et al., have been equipped with wires embedded in the hood of the incubator in order to radiate energy to the infant. Such arrangements have the disadvantage that the wires are opaque to X-rays, and interfere with visual inspection of the infant. Other incubators have been equipped with a plastic hood coated with an electrically conductive material, such as shown in U.S. Pat. No. 3,878,361--Levin et al. The coatings used have heretofore not been colorless. The coatings used generally have a yellow tint. This yellow tint causes difficulty in judging bilirubin levels in an infant making visual assessment of cyanosis more difficult.